A status of a moving article such as rotary angle or revolution of a rotating article has been detected by an apparatus as shown in FIG. 4. The rotating article 15 rotating about a rotary shaft 14 has teeth 15.sub.1 uniformly on the periphery thereof and two detectors 16a and 16b are disposed close to the teeth of the rotating article 15 to generate rotating signals in accordance with the teeth in a optical or magnetic manner. The detectors 16a and 16b are disposed in an offset manner by 90 degrees relative to the teeth 15.sub.1 to also detect a rotary direction of the rotating article.
However, rotation detecting signals comprising two value signals of "H" and "L" detected by the detectors 16a and 16b sometimes include chattering noise when the status is reversed, which causes the rotary angle of the rotating article (including the revolution thereof) to be detected, with the result that the two-phase encoder erroneously counts the detecting pulse signals.
In a prior art, there has been tried a method of reforming the signals by a Schmitt trigger circuit after a frequency range of noise component is removed from the signals by a low-pass filter.
In such a method, however, not only the countable frequency is lowered, but also erroneous pulses occur in accordance with the status of operation, all of which is disadvantageous for the two-phase encoder circuit.